Mechanism to shift the head span of a tape head at a wafer level

ABSTRACT

Provided are a magnetic tape head, a magnetic tape drive, and a computational device in which the magnetic tape head is comprised of a plurality of elements, wherein a pitch between adjacent elements of the plurality of elements is not identical. Selected elements of the plurality of elements that are shifted from a nominal position are selected in a symmetrical manner in the plurality of elements. A total of shifts of the elements of the plurality of elements that are shifted add up to a desired total shift to realign a plurality of modules, such that the median head span of each module type match as closely as possible to a desired value of a head span for all module types.

BACKGROUND

Embodiments relate to a mechanism to shift the head span of a tape headat a wafer level.

In magnetic media, data is typically stored as magnetic transitions,e.g., data is magnetically recorded on a surface of the magnetic media.The data stored is typically arranged in data tracks. A typical magneticstorage medium, such as a magnetic tape, includes a plurality of datatracks.

A tape head is a type of transducer used to convert electronic data intomagnetic bits to store the information. The tape is magnetized in apattern. The tape moves across a read/write head, with the tape headsurface in contact with the magnetic tape media being called the TapeBearing Surface (TBS). Inductive writers write magnetic transitions (orbits) to the magnetic surface of the tape. The Read elements may beinductive or magnetoresistive (MR) sensors which convert the magneticbits into electrical signals which can be converted to data bits usingprocess electronics in the tape drive containing the tape head.Transducer (read/write) heads are positioned relative to the data tracksto read/write data along the tracks. Accordingly, a tape head locateseach data track and accurately follows the path of the data track. Toachieve this, servo techniques have been developed which allow for aprecise positioning of the tape head relative to the data tracks. Onesuch technique makes use of servo patterns, that is, patterns of signalsor recorded marks on the medium, which are tracked by the head. Theservo patterns are recorded on the tape in order to provide a positionreference for the data tracks. Read operations on magnetic tapes areperformed by read heads, whereas write operations on magnetic tapes areperformed by write heads.

Writing and reading simultaneously of several tracks in parallel is awidely used approach how to achieve both high area densities and highdata rates. A plurality of read and write and servo elements are presentin a tape head for reading and writing data on tape. The write elements,the read elements, and the servo elements are all fabricated on anon-magnetic substrate referred to as a chip of wafer. The writeelements, the read elements and the servo elements may also be referredto as write heads, read heads, and servo heads respectively.

SUMMARY OF THE PREFERRED EMBODIMENTS

Provided are a magnetic tape head, a magnetic tape drive, and acomputational device in which the magnetic tape head is comprised of aplurality of elements, wherein a pitch between adjacent elements of theplurality of elements is not identical.

In certain embodiments, the plurality of elements comprise readers orwriters, or both readers and writers.

In further embodiments, selected elements of the plurality of elementsthat are shifted from a nominal position are selected in a symmetricalmanner in the plurality of elements.

In yet further embodiments, a total of shifts of the elements of theplurality of elements that are shifted add up to a desired total shiftto realign a plurality of modules, such that the median head span ofeach module type match as closely as possible to a desired value of thehead span for all module types.

In additional embodiments, wherein a head span is increased by multiplesof a minimum step size while realigning the plurality of modules suchthat the median head span of each module type match as closely aspossible to a desired value of the head span for all module types.

In yet additional embodiments, a group of elements of the plurality ofelements has a different pitch or separation from other groups ofelements.

In yet certain embodiments, the magnetic tape head containssymmetrically located servo elements such that a servo-to-servoseparation of the symmetrically located servo elements are within 50 nmof an ideal or specified value, wherein the servo-to-servo separation isthe head span.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the drawings in which like reference numbers representcorresponding parts throughout:

FIG. 1 illustrates a block diagram of a computing environment comprisinga tape drive including tape heads that are used to read data from a tapeand to write date to a tape, where the tape drive is coupled to acomputational device, in accordance with certain embodiments;

FIG. 2 illustrates a block diagram that shows a schematic diagram ofelement pitch and track pitch in a configuration of read and writeelements in the tape heads, in accordance with certain embodiments;

FIG. 3 illustrates a block diagram that shows configuration of elementsin tape heads, in accordance with certain embodiments;

FIG. 4 illustrates a table that shows the pitch for an example design;

FIG. 5A and FIG. 5B show a block diagram that shows first exemplaryoptions for shifting elements, in accordance with certain embodiments;

FIG. 6A and FIG. 6B show a block diagram that shows second exemplaryoptions for shifting elements, in accordance with certain embodiment

FIG. 7A and FIG. 7B show a block diagram that shows second exemplaryoptions for shifting elements, in accordance with certain embodiments;and

FIG. 8 illustrates a block diagram that shows certain elements that maybe included in the tape drive or a computational device described inFIGS. 1-7 , in accordance with certain embodiments.

DETAILED DESCRIPTION

In the following description, reference is made to the accompanyingdrawings which form a part hereof and which illustrate severalembodiments. It is understood that other embodiments may be utilized andstructural and operational changes may be made.

Embodiments described in this disclosure relate to a mechanism to shiftthe head span of a tape head at a wafer level. Elements such as readelements or write elements are symmetrically shifted to achieve anoverall shift in head span to match a desired value of head span asclose as possible. The need for symmetry is present, so that whenaligning the read/write elements during read/write operations themultiplicity of read/write elements will be as close to centered forboth read and write operations. The read or write elements are shiftedduring fabrication so that the head span is identical for both, while atthe same time complying with the constraint that while shifting, a headspan is increased by multiples of a predetermined minimum step sizewhile realigning the plurality of modules in a tape head to haveidentical head span.

FIG. 1 illustrates a block diagram of a computing environment 100comprising a tape drive 102 including tape heads 104 that are used toread data from a tape 106 and to write date to a tape 106, where thetape drive 102 is coupled to a computational device 108, in accordancewith certain embodiments.

The tape drive 102 that uses tapes 106 includes a controller 110 thatcontrols the operations of a write elements 112, read elements 114, andservo elements 116 that are read elements used for servo. The writeelements 112, the read elements 114, and the servo elements 116 may bereferred to as data write heads or write heads, data read heads or readheads, and servo heads respectively.

The tape 106 is inserted in the tape cartridge 108 of the tape drive102. The controller 110 of the tape drive 102 uses the servo elements toread servo patterns written on the tape 106 and then in response to aninput/output (I/O) operation received from a computational device 108performs read operations from the tape 106 with the read elements 114and write operations from the tape 106 with the write elements 112,where the computational device 108 may include any suitablecomputational device known in art, such as, a personal computer, aworkstation, a server, a mainframe, a hand held computer, a palm topcomputer, a telephony device, a network appliance, a blade computer, aprocessing device, a storage controller, etc.

FIG. 2 illustrates a block diagram 200 that shows a schematic diagram ofelement pitch and track pitch in a configuration of read and writeelements in the tape heads 104, in accordance with certain embodiments.The element pitch and track pitch are not drawn to scale, but theirrelative dimensions are shown.

Tape heads 104 contain multiple read elements and write elements tosimultaneously write and/or read multiple tracks simultaneously. Aplurality of write elements 202, 204 and a plurality of read elements206, 208 on the tape heads 104 are shown in FIG. 2 .

The pitch 210, or spacing between elements, (EP ) is conventionally thesame between elements and for processing reasons, is large relative tothe pitch of the tracks 212, 214 written on the magnetic media, TP 216as shown in FIG. 2 . The tape passes under the read and write elementsto have tracks written on them first in one direction and then inanother direction.

The physical element containing the read and write elements when cut outfrom a wafer is sometimes called a chip at the wafer level and a modulewhen attached to a substrate used for building into a head. The read andwrite chips also contain read elements called servos used to steer thechip and keep the read and write elements aligned properly to maintainthe written track spacing or to remain aligned over the written trackduring read-back. The servos read pre-written “servo patterns” writtenon the tape.

In FIG. 2 , the reader width 218 that indicates the width of a readelement and the write width 220 that indicates the width of a writeelement are shown.

FIG. 3 illustrates a block diagram 300 that shows configuration ofelements in tape heads, in accordance with certain embodiments.

In one conventional design, the servos are aligned outside the read orwrite elements. For example, block 302 shows a reader and servoconfiguration with N read elements R01 304, R02 306,..., RN 308, and twoservos S01 310, S02 312, where the alignment of the servos and readelements in consecutive order are S01, R01, R02, ..., RN, S02, where S01and S02 are the two servos and RM is the M^(th) read element, as shownin FIG. 3 .

For writer chips (modules), the read elements are replaced by writeelements, WM. For example, block 314 shows a writer and servoconfiguration with N write elements W01 316, W02 318,..., WN 320, andtwo servos S01 322, S02 324, where the alignment of the servos and writeelements in consecutive order are S01, W01, W02, ..., WN, S02, where S01and S02 are the two servos and WM is the M^(th) write element, as shownin FIG. 3 .

In certain embodiments, for processing reasons, the element pitch, EP,is much greater than the track pitch, TP, so EP » TP. For example, EPmay be on the order of 100 µm (1E-4 m) while the TP may be on the orderof 1 µm (1000 nm). The difference between the TP and the reader width,W_(r), may be on the order of 100 to 400 nm (TP — W_(r)). For a readelement centered on the written track the separation between the edge ofthe read element and the edge of the written track, FE, is:

$\text{FE =}\left( \frac{TP - W_{r}}{2} \right)$

. The head span, HS, 326, 328 from S01 to S02 is of the order of HS =(N + 1) · EP, where in FIG. 3 the head span for the reader module isshown via reference numeral 326 and the head span for the writer moduleis shown via reference numeral 328. With N on the order of 30 elements,the HS is on the order of 3.2 mm (31·0.1 mm), or 1000 times theseparation of the edge of a perfectly centered reader from the edge of aperfectly written data track.

Developing features on a wafer has limitations in step sizes which is onthe order of 10 s of nm. If, for example, the necessary shift in span is200 nm and the minimum step size is 10 nm (Δ_(StepMin)=10 nm) and thereare 35 elements (N_(element)) on the chip, then the allowed change inhead span (ΔSpan) is in increments of 340 nm (ΔSpan = (N_(element) - 1)· Δ_(StepMin)), which is too coarse for the needed shift of 200 nm.During fabrication of heads the head span needs to be adjusted to alignthe reader and writers.

Certain embodiments, provide mechanism is needed to adjust the head spanat the wafer to shift the span by levels of the order of 100 nm.

Another means to improve tolerance to head span shifts, termed scaledheads, uses a strategy which maintains the same pitch between readertracks and shifts the read track width from the center to the outer readelement, with the center read track being the widest and the outertracks the narrowest. The scaled head approach does not change theoverall pitch as in certain embodiments provided in this disclosure Thescaled head approach also decreases the error-rate performance of thenarrower reader.

Certain embodiments provide mechanisms to shift the overall head span bydistances of ΔSpan_(Required) < (N_(elemet) - 1) · Δ_(PitchMin) to makea shift not for every element, but in steps. For example, stepping everyother element by Δ_(PitchMin.) This may cut the adjusted head span inhalf.

FIG. 4 illustrates a table (Table 1 shown by reference numeral 400) thatshows the pitch for an example design.

The total head span is defined as the separation between the two endservos, S01 and S02. In the examples to be provided below, there are 33readers with an initial pitch given in Table 1 400. S01 and S02 are thetwo end servos and Rn are reader or writer elements in this example from1 to 33. The pitch between two consecutive reader elements is 85 µm(shown via reference numeral 402) and the pitch between servo S0 andreader R01 is the same as the pitch between reader R33 and servo S02 andequals 100 µm (as shown via reference numeral 404).

The minimum feature shift for the wafer stepper, Δ_(StepMin), is takenas 20 nm. So, if all elements are stepped by the minimum feature, with33 read and 2 servo elements, N_(element) = 35, and the minimum changein span shift, ΔSpan_(min,) would be 680 nm: ΔSpan_(Min) =(N_(element) - 1) · Δ_(StepMin·)

With the pitch values given in Table 1 of FIG. 4 , the total head spanis 2,920 ,000 nm.

In certain embodiments, to change the head span by values less than theis to shift some tracks, but not all tracks. The center element, R17will remain centered, and the shifts will be done symmetrically aboutR17.

FIG. 5 shows a block diagram 500 that shows first exemplary options forshifting elements, in accordance with certain embodiments.

Options 1a 502 and 1b 504 show examples of a span shift, ΔSpan, of 80 nmwhile Options 2a 506 and 2b 508 show examples of 120 nm shiftsrespectively. For the options, the servo elements are S01 or S02 andreader (writer) elements are R01 to R33. Pitch_0 (reference numeral 510)is the initial pitch (i.e., the pitch in the absence of the shift), andΔPitch (reference numeral 512) gives the change in pitch for the givenelement relative to Pitch_0. Pitch_N(reference numeral 514) is the newpitch after the change in pitch, (i.e., Pitch_N = Pitch_0 + ΔPitch).

In the examples, the desired span change is higher by 80 nm for Options1a and 1b and 120 nm for Options 2a and 2b. If the shift in span werenegative, the sign of ΔPitch would be negative. The total change in headspan is:

ΔSpan = N_(elementShift) ⋅ ΔPitch

For the 80 nm shift, N_(elementShift) is 4 and for the 120 nm shift,N_(elementShift) is 6. To ensure symmetry, N_(elementShift) is an evennumber.

It should be noted that in FIG. 5 , the reader R17 is in the center. Inoption 1a shifts are made to readers R01, R09, R25 and R33 and in option1b similar shifts are made to readers R04, R11, R22, R29. The selectionof readers for shifting may be performed experimentally. The total shiftin option 1a and 1b is 80 nm, whereas the total shift in option 2a, 2bis 120 nm. Instead or shifting readers, in alternative embodimentswriters could be shifted as needed.

FIG. 6 shows a block diagram 600 that shows second exemplary options(option 3 603) for shifting elements, in accordance with certainembodiments. Option 3 shows an example of a span shift, ΔSpan, of 160nm. It can be seen that 8 reader elements have been shifted by 20 nm toincrease head span by 160 nm, where shift can only per performed inmultiples of a minimum of 20 nm.

FIG. 7 shows a block diagram 700 that shows second exemplary options(option 4a 702, 4b 704, 4c 706) for shifting elements, in accordancewith certain embodiments. Options 4a-c show examples of a span shift,ΔSpan, of 200 nm. It can be seen that 10 reader elements have beenshifted by 20 nm to increase head span by 200 nm, where shift can onlyper performed in multiples of a minimum of 20 nm.

Option 4a 702 spreads the spacing out across the entire width. In option4a, the shifts start with the 2^(nd) elements from the center (R15 andR19), and then steps every 4^(th) element until the servos. Options 4band 4c maintain the location of the change in step constant at every3^(rd) element, but move the location where the 1^(st) step occursfurther from the center at the 3^(rd) and 4^(th) element from the centeras the first change in step. In can be seen that different combinationsof readers may be shifted in different embodiments.

Therefore FIGS. 1-7 illustrate certain embodiments in which elements areshifted symmetrically to align read heads to write heads to account forchange in head span. The magnetic tape head is comprised of a pluralityof elements, wherein a pitch between adjacent elements of the pluralityof elements is not identical and the plurality of elements comprisereaders or writers.

While ideally all modules should have identical head spans, this is notphysically possible. Furthermore, the minimum resolution is twice theminimum step size. The modules will have a distribution of head spans.For example, the reader modules, RM, have a nominal head span of 3000 µmand the writer modules, WM, have a nominal head span of 3200 µm. The WMand RM may both have a range of +/- 150 µm, so the WM would span from3050 to 3350 µm and the RM would span from 2850 to 3150 µm. The desiredshift needed would be -200 µm to the WM to match with the nominal of theRM. With the shift, both WM and RM would have a nominal HS of 3000 µm,and would both range from 2850 to 3150 µm. Also it is to be noted, thatfor a minimum step size of 20 nm, the minimum resolution for shifting amodule head span would be 2x20 or 40 nm. Since there is a minimum stepsize and embodiments make the shift symmetric, then the modules cannotbe aligned better than within twice of the minimum step size.

A total of shifts of the elements of the plurality of elements that areshifted add up to a desired total shift to realign a plurality ofmodules, such that a median head span of each module type match as closeas possible to a desired value the head span for all module types. Themedian head span is the median of all head spans of the plurality ofmodules.

A head span is increased by multiples of a minimum step size whilerealigning the plurality of modules such that a median head span of eachmodule type match as close as possible to a desired value the head spanfor all module types.

A group of elements of the plurality of elements may have a differentpitch or separation from other groups of elements. The magnetic tapehead may be comprised of servo elements that that are located within atmost 50 nm of an ideal or specified location of servos.

In certain embodiments, the magnetic tape head contains symmetricallylocated servo elements such that a servo-to-servo separation of thesymmetrically located servo elements are within 50 nm of an ideal orspecified value, wherein the servo-to-servo separation is the head span.While less than 50 nm is preferred, the maximum tolerable limit is 50nm, and embodiments try to locate the servo elements within (i.e., lessthan or equal to) 50 nm.

Additional Embodiment Details

The described operations may be implemented as a method (e.g., tosimulate the design of the apparatus), apparatus, or computer programproduct (e.g., to simulate the design of the apparatus) using standardprogramming and/or engineering techniques to produce software, firmware,hardware, or any combination thereof. Accordingly, aspects of theembodiments may take the form of an entirely hardware embodiment, anentirely software embodiment (including firmware, resident software,micro-code, etc.) or an embodiment combining software and hardwareaspects that may all generally be referred to herein as a “circuit,”“module” or “system.” Furthermore, aspects of the embodiments may takethe form of a computer program product. The computer program product mayinclude a computer readable storage medium (or media) having computerreadable program instructions thereon for causing a processor to carryout aspects of the present embodiments.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present embodiments may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Smalltalk, C++ or the like, andconventional procedural programming languages, such as the “C”programming language or similar programming languages. The computerreadable program instructions may execute entirely on the user’scomputer, partly on the user’s computer, as a stand-alone softwarepackage, partly on the user’s computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer may be connected to the user’s computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).In some embodiments, electronic circuitry including, for example,programmable logic circuitry, field-programmable gate arrays (FPGA), orprogrammable logic arrays (PLA) may execute the computer readableprogram instructions by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present embodiments.

Aspects of the present embodiments are described herein with referenceto flowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instruction.

FIG. 8 illustrates a block diagram that shows certain elements that maybe included in the tape drive 102 or the computational device 108 or thecontroller 110, in accordance with certain embodiments. The system 800may include a circuitry 802 that may in certain embodiments include atleast a processor 804. The system 800 may also include a memory 806(e.g., a volatile memory device), and storage 808. The storage 808 mayinclude a non-volatile memory device (e.g., EEPROM, ROM, PROM, flash,firmware, programmable logic, etc.), magnetic disk drive, optical diskdrive, tape drive, etc. The storage 808 may comprise an internal storagedevice, an attached storage device and/or a network accessible storagedevice. The system 800 may include a program logic 810 including code812 that may be loaded into the memory 806 and executed by the processor804 or circuitry 802. In certain embodiments, the program logic 810including code 812 may be stored in the storage 808. In certain otherembodiments, the program logic 810 may be implemented in the circuitry802. One or more of the components in the system 800 may communicate viaa bus or via other coupling or connection 814. Therefore, while FIG. 8shows the program logic 810 separately from the other elements, theprogram logic 810 may be implemented in the memory 806 and/or thecircuitry 802.

Certain embodiments may be directed to a method for deploying computinginstruction by a person or automated processing integratingcomputer-readable code into a computing system, wherein the code incombination with the computing system is enabled to perform theoperations of the described embodiments.

The terms “an embodiment”, “embodiment”, “embodiments”, “theembodiment”, ”the embodiments”, “one or more embodiments”, “someembodiments”, and “one embodiment” mean “one or more (but not all)embodiments of the present invention(s)” unless expressly specifiedotherwise.

The terms “including”, “comprising”, “having” and variations thereofmean “including but not limited to”, unless expressly specifiedotherwise.

The enumerated listing of items does not imply that any or all of theitems are mutually exclusive, unless expressly specified otherwise.

The terms “a”, “an” and “the” mean “one or more”, unless expresslyspecified otherwise.

Devices that are in communication with each other need not be incontinuous communication with each other, unless expressly specifiedotherwise. In addition, devices that are in communication with eachother may communicate directly or indirectly through one or moreintermediaries.

A description of an embodiment with several components in communicationwith each other does not imply that all such components are required. Onthe contrary a variety of optional components are described toillustrate the wide variety of possible embodiments of the presentinvention.

Further, although process steps, method steps, algorithms or the likemay be described in a sequential order, such processes, methods andalgorithms may be configured to work in alternate orders. In otherwords, any sequence or order of steps that may be described does notnecessarily indicate a requirement that the steps be performed in thatorder. The steps of processes described herein may be performed in anyorder practical. Further, some steps may be performed simultaneously.

When a single device or article is described herein, it will be readilyapparent that more than one device/article (whether or not theycooperate) may be used in place of a single device/article. Similarly,where more than one device or article is described herein (whether ornot they cooperate), it will be readily apparent that a singledevice/article may be used in place of the more than one device orarticle or a different number of devices/articles may be used instead ofthe shown number of devices or programs. The functionality and/or thefeatures of a device may be alternatively embodied by one or more otherdevices which are not explicitly described as having suchfunctionality/features. Thus, other embodiments of the present inventionneed not include the device itself.

At least certain operations that may have been illustrated in thefigures show certain events occurring in a certain order. In alternativeembodiments, certain operations may be performed in a different order,modified or removed. Moreover, steps may be added to the above describedlogic and still conform to the described embodiments. Further,operations described herein may occur sequentially or certain operationsmay be processed in parallel. Yet further, operations may be performedby a single processing unit or by distributed processing units.

The foregoing description of various embodiments of the invention hasbeen presented for the purposes of illustration and description. It isnot intended to be exhaustive or to limit the invention to the preciseform disclosed. Many modifications and variations are possible in lightof the above teaching. It is intended that the scope of the invention belimited not by this detailed description, but rather by the claimsappended hereto. The above specification, examples and data provide acomplete description of the manufacture and use of the composition ofthe invention. Since many embodiments of the invention can be madewithout departing from the spirit and scope of the invention, theinvention resides in the claims hereinafter appended.

IBM, z/OS, zSeries, pSeries, xSeries, BladeCenter, WebSphere, and DB2are trademarks of International Business Machines Corporation registeredin many jurisdictions worldwide.

1. A magnetic tape head, comprising: a plurality of elements, wherein apitch between adjacent elements of the plurality of elements is notidentical, wherein selected elements of the plurality of elements thatare shifted from a nominal position are selected in a symmetrical mannerin the plurality of elements, and wherein a total of shifts of theelements of the plurality of elements that are shifted add up to adesired total shift to realign a plurality of modules, such that amedian head span of each module type match as close as possible to adesired value of a head span for all module types.
 2. The magnetic tapehead of claim 1, wherein the plurality of elements comprise readers orwriters, or both readers and writers. 3-4. (canceled)
 5. The magnetictape head of claim 2, wherein a head span is increased by multiples of aminimum step size while realigning the plurality of modules such thatthe median head span of each module type match as closely as possible tothe desired value the head span for all module types.
 6. The magnetictape head of claim 5, wherein a group of elements of the plurality ofelements has a different pitch or separation from other groups ofelements.
 7. The magnetic tape head of claim 6, wherein the magnetictape head contains symmetrically located servo elements such that aservo-to-servo separation of the symmetrically located servo elementsare within 50 nm of an ideal or specified value, and wherein theservo-to-servo separation is the head span.
 8. A magnetic tape drive,comprising: a receptacle for magnetic tape; and a magnetic tape head toread and write on the magnetic tape, the magnetic tape head, comprising:a plurality of elements, wherein a pitch between adjacent elements ofthe plurality of elements is not identical, wherein selected elements ofthe plurality of elements that are shifted from a nominal position areselected in a symmetrical manner in the plurality of elements, andwherein a total of shifts of the elements of the plurality of elementsthat are shifted add up to a desired total shift to realign a pluralityof modules, such that a median head span of each module type match asclose as possible to a desired value of a head span for all moduletypes.
 9. The magnetic tape drive of claim 8, wherein the plurality ofelements comprise readers or writers, or both readers and writers.10-11. (canceled)
 12. The magnetic tape drive of claim 9, wherein a headspan is increased by multiples of a minimum step size while realigningthe plurality of modules such that the median head span of each moduletype match as closely as possible to the desired value the head span forall module types.
 13. The magnetic tape drive of claim 12, wherein agroup of elements of the plurality of elements has a different pitch orseparation from other groups of elements.
 14. The magnetic tape drive ofclaim 13, wherein the magnetic tape head contains symmetrically locatedservo elements such that a servo-to-servo separation of thesymmetrically located servo elements are within 50 nm of an ideal orspecified value, and wherein the servo-to-servo separation is the headspan.
 15. A computational device, comprising: a processor; a tape drivecoupled to the processor; and a magnetic tape head in the tape drive toread and write on a magnetic tape in the tape drive, the magnetic tapehead, comprising: a plurality of elements, wherein a pitch betweenadjacent elements of the plurality of elements is not identical, whereinselected elements of the plurality of elements that are shifted from anominal position are selected in a symmetrical manner in the pluralityof elements, and wherein a total of shifts of the elements of theplurality of elements that are shifted add up to a desired total shiftto realign a plurality of modules, such that a median head span of eachmodule type match as close as possible to a desired value of a head spanfor all module types.
 16. The computational device of claim 15, whereinthe plurality of elements comprise readers or writers, or both readersand writers. 17-18. (canceled)
 19. The computational device of claim 16,wherein a head span is increased by multiples of a minimum step sizewhile realigning the plurality of modules such that the median head spanof each module type match as closely as possible to the desired valuethe head span for all module types.
 20. The computational device ofclaim 19, wherein a group of elements of the plurality of elements has adifferent pitch or separation from other groups of elements.
 21. Thecomputational device of claim 20, wherein the magnetic tape headcontains symmetrically located servo elements such that a servo-to-servoseparation of the symmetrically located servo elements are within 50 nmof an ideal or specified value, and wherein the servo-to-servoseparation is the head span.